1. Field of the Invention
This invention relates to a method of mounting a printed circuit board in a casing, and more specifically to a method of mounting a printed circuit board into a radio frequency shielding casing, the casing having an electrically conducting surface, and securing the earthing between the printed circuit board and the casing.
2. Description of the Prior Art
Electronic equipment operating in the radio frequency range is conventionally installed in metal casings, in order to ensure a shielded environment free of interference from the outside and also to prevent the equipment itself from radiating disturbances to the environment. There may be several units in the same casing, which then is divided into compartments by walls. Usually, in order to ensure a good radio frequency shielding, the casing and the compartments are closed with a metal lid, a sealing strip of electrically conducting material running between the edges of the casing and the lid.
The earthing of the printed circuit boards is conventionally provided by a contact between the earthing strip on the printed circuit board and the casing. This is in most cases feasible at those points where the board is fastened to the casing, e.g. by screws. Alternative earthing contacts have been made with other mechanical arrangements, such as springs, clips and the like.
The conventional mounting methods then need space on the printed circuit boards for screws and the like, which reduces the available space for components, or necessitates correspondingly larger printed circuit boards. On the other hand, the fastening by screws traditionally requires special studs to be molded in the casing and provided with threading for the fastening screws.
The conventional mounting methods require many separate components many manufacturing phases, including precision machining and manual work.